LONDON (AP) — King Charles III was crowned Saturday at Westminster Abbey, in a ceremony built on ancient traditions at a time when the British monarchy faces an uncertain future.

Trumpets sounded inside the medieval abbey and the congregation shouted “God save King Charles” as the ceremony began in front of more than 2,000 guests, including world leaders, aristocrats and celebrities. Outside, thousands of troops, tens of thousands of spectators and a smattering of protesters converged along a route that the king travelled from Buckingham Palace in a gilt-trimmed, horse-drawn carriage.

It was the final mile of a seven-decade journey for Charles from heir to monarch.

To the royal family and government, the occasion — code-named Operation Golden Orb — is a display of heritage, tradition and spectacle unmatched around the world.

The rite was expected to by watched by millions, though the awe and reverence the ceremony was designed to evoke are largely gone — and many greeted the day with apathy.

Some even met it with disdain. Republican protesters gathered outside to holler “ Not my king ” for a celebration of an institution they say stands for privilege and inequality, in a country of deepening poverty and fraying social ties. A handful were arrested.

As guests arrived, the church buzzed with excitement and was abloom with fragrant flowers and colourful hats. Among them were US First Lady Jill Biden, French President Emmanuel Macron, Canadian Prime Minister Justin Trudeau, eight current and former British prime ministers as well as Judi Dench, Emma Thompson and Lionel Richie.

Thousands of people from across the UK and around the world camped overnight along a 1.3-mile (2-kilometre) route that the king and his wife, Camilla, travelled to reach the abbey.

At a traditional Anglican service slightly tweaked for modern times, Charles, clad in crimson and cream robes, swore on a Bible that he is a “true Protestant.”

But for the first time, a preface was added to the coronation oath to say the Church of England “will seek to foster an environment where people of all faiths and beliefs may live freely,” and the epistle from the King James Bible was read by Prime Minister Rishi Sunak, Britain’s first Hindu leader.

A gospel choir performed a newly composed “Alleluia,” and, for the first time, female clergy took part in the ceremony.

For 1,000 years and more, British monarchs have been crowned in grandiose ceremonies that confirm their right to rule.

These days, the king no longer has executive or political power, and the service is purely ceremonial since Charles automatically became king upon death of his mother, Queen Elizabeth II, in September.

The king remains the UK’s head of state and a symbol of national identity — and Charles will have to work to unite a multicultural nation and keep the monarchy relevant at at time when support for it is waning, especially among younger people.

The anti-monarchy group Republic said six of its members, including its chief executive, were arrested as they arrived at a protest. Police have said they will have have a “low tolerance” for people seeking to disrupt the day, sparking criticism that they are clamping down on free speech.

A cost-of-living crisis is also making everyone in the UK poorer, raising questions about the cost of all the pomp.

Charles has sought to lead a smaller, less expensive royal machine for the 21st century. So this will be a shorter affair than Elizabeth’s three-hour coronation.